The present invention relates to a method and apparatus for transferring wet plastic objects, such as contact lenses, from one station to another.
The molding of hydrophilic contact lenses is known. Various processes are disclosed in U.S. Pat. No. 4,495,313 to Larsen; U.S. Pat. No. 4,640,489 to Larsen, et al.; U.S. Pat. No. 4,680,336 to Larsen et al.; U.S. Pat. No. 4,889,664 to Larsen et al.; and U.S. Pat. No. 5,039,459 to Larsen et al., all of which are assigned to the assignee of the present invention.
These prior art references disclose a contact lens production process wherein each lens is formed by molding a reactive mixture between a front curve (lower mold section) and back curve (upper mold section). Typically, the lenses are carried in a mold array or pallet, such as a two-by-four array. While in between the front and back curves, the monomer is polymerized to form the lens. In one type of process, the lens is removed from the front curve mold during a hydration step and then washed by the application of a hydrating deionized (DI) water to remove processing chemicals, e.g. diluents, from the lens.
Sometimes, when deionized water is used in the hydration, the final step of the process is to introduce a buffered saline solution into the final package holding the lens, and then seal the lens within the package so that the final lens equilibrium (ionic neutralization, final hydration and final lens dimensioning) is accomplished in the package at room temperature or during sterilization. U.S. Pat. No. 4,961,820, also assigned to the assignee of the present invention, discloses a final package for a contact lens, wherein the package is formed from a transparent plastic material such as polypropylene and a foil laminate that is heat sealed thereto.
The transfer of soft contact lenses during manufacture has been a significant problem. The lenses are small, are nearly invisible and are particularly hard to handle when immersed in the fluids commonly used in the manufacturing process. Accurate and reliable transfer of the wet lenses from one location to another or to a final package is often necessary during the manufacturing process.
As apparent from the foregoing, a need exists for an apparatus to transfer wet lenses from one station, such as a mold or hydrating bath, to another station, such as a package, and at the same time to remove or reduce the amount of the hydrating liquid and other material present on the lens from the hydrating process.
U.S. Pat. No. 5,578,331, entitled xe2x80x9cAutomated Apparatus and Method for Preparing Contact Lenses for Inspection and Packagingxe2x80x9d, also assigned to the assignee of the present invention, discloses a robotic arm for transferring a plurality of soft contact lenses from a first processing station to a second processing station. The robotic device includes an adjustable array of convex contact lens carriers. The specification of U.S. Pat. No. 5,578,331 is herein incorporated by reference.
U.S. Pat. No. 5,561,970, which also is owned by the assignee of this application, discloses an automatic contact lens transfer system, comprising robotic arms to contact and transfer soft contact lenses. The ""970 patent is hereby incorporated by reference. U.S. Pat. No. 5,706,634, which also is owned by the assignee of this application, discloses a contact lens transfer device which comprises a convex lens transfer surface onto which the lens is secured via surface tension. The device then transports the lens to a second location. The lens is removed from the convex lens transfer surface when an amount of deionized water is ejected from the device. The ""634 patent is hereby incorporated by reference. However, neither of these patents teach the removal of the hydrating solution or other matter, nor are they capable of performing the function of transfer and controlled matter removal. In addition, prior contact lens transfer systems fail to address splatter of liquid from a lens onto the packaging during lens transfer.
The invention is concerned with the withdrawal of excess or foreign matter from a wet object, such as a contact lens, and/or its packaging prior to being sealed in a package. In preferred embodiments, this is achieved by providing a hood around a probe which is used to pick up and later release the wet object. The probe preferably handles the wet object using positive and negative pressure. The hood encompassing the probe creates suction to control matter during deposition and matter withdrawal or removal.
In one respect, the invention is directed to a method and apparatus for transferring a wet object, such as a contact lens, during and between various steps of manufacture and packaging. One set of these manufacturing steps is disclosed in U.S. Ser. No. 09/252,307, filed herewith in which transfer is necessary from a station at which washing and hydration of the lens takes place, in a front curve mold, to a final package designed for customer use. Alternatively, this apparatus could be used to transfer a lens from a reusable mold to a contact lens package, or from a mold to a container for inspection of the contact lens, or from any other first position to a second position.
In a preferred embodiment, the invention comprises a probe with a perforated hemispherical nozzle head having a diameter and shape corresponding to the contact lens shape. The probe is moved into close proximity, and more preferably into contact with the lens"" concave surface while in a carrier or holder, such as a front curve mold, and picks up the contact lens from the holder by vacuum force, which creates suction at the nozzle which draws the lens from the holder onto the probe hemispherical nozzle.
A hood assembly encompasses the lower end of the probe and is resiliently biased to exert downward pressure preferably via holding pins on the carrier or holder, e.g., front curve, from which the lens is being removed to hold it in place against the vacuum force as the lens is being removed from the front curve mold
The probe is then relocated over the carrier or package into which the lens is to be deposited. In a preferred mode, once the lens is lifted by the probe out of the front curve mold, the vacuum is shut off, with the lens being held by surface tension while the probe is relocated over the carrier or package. Alternatively, the vacuum force supply can be shut off after the probe has been positioned over the carrier or package. Preferably, the hood is pressed against the carrier or package, holding it in place, and if a package, the hood is designed to protect the sealing area from splashing. Once in the proper location, one or more short, controlled pressure pulses of liquid or gas, preferably air, are supplied. At the same time, preferably a vacuum is applied within more than one passage designed within an opening from the hood assembly. As a result, the contact lens is ejected from the probe into the package by at least one pressure pulse, and any residual washing solution or other material on the lens or packaging which is displaced from the contact lens by the pressure pulse(s) or movement of the lens off the probe is drawn into the passage of the hood by the vacuum. This results in rapid placement of the contact lens into the final package without excess matter on the lens or the package. The vacuum draws away any excess matter which becomes airborne during the ejecting step, and preferably the vacuum also removes any matter in the heat seal area of the package to provide for successful package closure.
Presence of the lens during transfer can be detected by measurement of the vacuum that is achieved. A low vacuum indicates that there is no lens carried by the probe.
In one respect, the invention provides a method for transferring a wet object from a first position to a second position. The method includes the steps of picking up an object from a first position with a nozzle, ejecting the object from the nozzle with a pressurized fluid to a second position, and drawing away any excess matter from the object which becomes airborne during the ejecting step. In a preferred mode, the drawing step commences before the ejecting step with the excess matter being drawn away from and external to the nozzle. The method may further include the step of providing a coating material to the object during the transfer process, with excess coating material being drawn away the same as any other excess matter. The object being transferred can be relocated to a different position by moving the nozzle after it is picked up, or the object can be relocated by moving a new container, for example, product packaging, under the nozzle while the nozzle remains stationary.
In another respect, the method of the invention transfers a wet object from a first container to a second container. This process includes the steps of locating a probe having a nozzle adjacent the object in the first container, creating a vacuum in the nozzle to draw the object to the nozzle, deactivating the vacuum, providing a pressurized fluid in the nozzle to release the object and to displace any excess matter from the object, and creating a vacuum within a hood disposed about the nozzle to draw away the any excess matter.
According to another aspect of the invention, an apparatus for transferring a wet object from a first station to a second station is disclosed. The apparatus includes a probe having a reciprocating barrel with a passage for communication with a positively or negatively pressurized fluid. A nozzle is affixed at one end of the probe for transferring the wet object from the first station to the second station, the nozzle being in communication with the passage. A variety of nozzles of different sizes and shapes can be affixed to the probe. A hood is disposed about the nozzle and is connectable to a vacuum source. Upon application of the pressurized fluid, e.g. gas or liquid, the wet object is released from the nozzle, thereby causing excess matter to be ejected from the wet object which is drawn away within the hood. In a preferred form, the hood includes spacers which depend therefrom and space the hood from the station that it contacts, for example, a front curve mold for a contact lens or a contact lens package. The spacers limit movement of the hood and ensure that an inflow passageway is available to cause air to rush over the station (e.g., the seal area of a package) and thereby dry the area surrounding the hood or maintain that area dry during the transfer of the wet object. The apparatus may further include a controller programmed to control the vacuum connection to the hood and the application of pressurized fluid to the probe, and control the movement of the assembly.
It is therefore an object of the invention to provide a method and apparatus for transferring wet flexible objects, such as contact lenses, from one station to another.
Another object is to provide a method and apparatus for pickup and transfer of wet flexible molded parts and removing the liquid and other matter, particularly from the surface of the molded parts, during the transfer.
An additional object is to provide a method and apparatus for transferring a wet object, such as a contact lens, from one station to another which uses a probe to remove the lens from the first station by vacuum pressure and transfer it to the second station where it is deposited by applying a pressurized stream or pulse of air or liquid through the probe to the object.
A further object is to provide a probe to transfer a wet lens from one position to another and to remove excess liquid or other matter from the lens surface during the transfer.
Yet a further object is to provide a method and apparatus for transferring a wet object which prevents contamination of the heat seal area of the package. In this design, the hood fits over the package to prevent contamination of the heat seal area.
Another object is to provide a probe which has a hood which prevents the pickup of the containers at the first and second stations.